This issue has been resolved in the most recent version of the Strava app. Update to version 150.0.1 or higher from the App Store and you should no longer experience crashes.
We're experiencing an issue that's preventing athletes using old versions of iOS from opening the Strava app. We are working on a fix but, in the meantime, you can update your iOS to version 12.2 or higher to resolve the issue. Here is more information on how to update your iOS.